Signaling system



Dec. 1, 1925 1,563,342

F. CONRAD S IGNALI NG SYSTEM Filed A ril 1922 2 Sheets-Sheet 1 mlmm v41%? I I 72 A? 2 INVENTOR Fw /r fol/rad.

: ATTORNEY Patented Dec. 1, 1925.

1,563,342 UNITED STATES PATENT OFFICE..

FRANK CONRAD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY. A CORPORATION OF PENNSYLVANIA.

SIGNALING SYSTEM.

Application filed i e 1, 1922. Serial No. 548,679.

7'0 071 whom 'ifimaq concern:

Be it known that I, FRANK CONRAD, a citizen of the United States, and aresident of Pittsburgh. in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in SignalingSystems, of which the following is a specification.

My invention relates to wireless transmission systems and moreespecially to oscillation generators adapted to be excited byalternating-current sources of energy.

One object of my invention is to provide an oscillation-generator systememploying vacuum tubes as oscillation generators which admits ofexcitation directly by alternating currents of commercial frequency.

Another object of my invention is to so embody a sustaining inductancein the alternating-current supply system for the oscillator tubes as tomaintain a substantially constant power supply to the oscillator tubes.

Inasmuch as it would require a sustaining inductance of infinite valuein the alternating-current mains to completely smooth out thefluctuations in the power supply to the oscillator tubes, it is apparentthat a residual fluctuation will remain.

A further object of my invention, therefore, is to eliminate theresidual fluctuations just mentioned, thereby adapting my system forwireless telephony.

A still further object of my invention is to .provide means whereby thegenerator system. may be rendered oscillatory or nonoscillatory, atwill, and, at the same. time, provide means for limiting the supplycurrents of the tubes to safe values, thereby adapting my system for thetransmission of wireless telegraph signals.

Other objects of my invention will appear more fully from the followingdescription of the nature, mode of operation and various applications ofmy invention.

Heretofore, when employing alternatingcurrent power for the excitationof oscillator-tube systems, it has been customary to employ a separateset of rectifier tubes. Such tubes are expensive and require care andattention, which is undesirable.

I find, however, that, by employing a system as hereinafter described,the rectitier tubes may be eliminated and the system may be energizeddirectly from the alterdesired result may be obtained by simultaneouslycontrolling, at will, the amount of grid-leak in the oscillatory circuitand the impedance of the alternating-current supplv circuit.

lVith these and other objects and applications in View, my inventionfurther consists in the mode of operation and the constructional detailshereinafter described and claimed and illustrated in the accompanyingdrawing, wherein:

Figure 1 is a diagrammaticview of a simplified wireless telephone systemembodying I my invention Fig. 2 is a similar view showing means forbalancing'out the residual power fluctuations obtaining in the previoussystem;

Fig. 3 is a similar view, but showing still another means for removingthe disturbing. effects of the residual power fluctuations;

' Fig. 4 is a View similar to that of Fig. l, but showing my system somodified as to admit of the transmission of wireless telegraph signals.

In Fig. 1, a pair of thermionic tubes 1 and 2. which are caused to serveboth as oscillation generators and as rectifiers, are shown ascomprising anodes 3 and 4, gridmembers 5 and G and hot cathodes 7 and 8,respectively, the latter being energized from a common source ofdirect-current energy 9. The tubes 1 and 2 may be successively energizedby alternate half cycles of an alternatingcurrent source of energy 11 ofcommercial frequency through a transformer 12. The anodes'3 and 4 areconnected to opposite terminals of a pair of series-connected secondarywindings 13 and 14-. of the transformer '12 by conductors, 15 and 16,respectively. The hot cathodes 7 and 8 are connected to the commonterminal17 of the'secondary windings 13 and 14 by a'conductor 18.Thep'rimary transformer windings 19 and 21 are serially connected to thesource of energy 11 by conductors 22 and 23, re-

spectively.

Inasmuch as the distributed capacity of the transformer windings 13 and14 may be of suflicient value to cause the dissipation of a considerableamount of radio-frequency energy therein, I have found it desirable toconnect radio-frequency choke coils 24 and 25 in the anode leads 15 and16, respectively.

The transformer 12 is so designed as to provide, for each anodeconductor, a sustaining inductance of suflicient value to maintain thecurrent in one conductor while that in the other conductor is buildingup to approximately its full value, that is to say, to so prolong thecurrents in each conductor that their sum is practically a constantquality at all times. One type of transformer for carrying the abovedesired result into effect is shown in my United States Patent No.931,114, filed January 10, 1908,

' and assigned to the Westinghouse Electric & Manufacturing Company, andhence a detailed description thereof is unnecessary.

The oscillation generator' system comprises the usual plate-filament andgridfilament circuit (onnections. The anodes 3 and 4 are connected to anadjustable tappoint 26 of an inductance coil 27 through condensers 28and 29, respectively. The condensers are provided in order to preventthe short-circuiting of the low-frequency currents. The filaments 7 and8 are connected, by a conductor 31, to an adjustable tap-point 32 of thetuning inductance coil 27. A conductor 33 serves to connect this pointto ground.

Grid elements 5 and 6 are connected, in parallel, to an adjustable tappoint 34 of the inductance coil 27 by a conductor 35. The conductor35-includes, in addition, a grid condenser 36 and a grid leak 37connected in shunt relation thereto and a secondary winding 38 of amodulating transformer 39, the primary winding 41 of which is seriallyincluded in a modulating circuit comprising, in addition, a source ofdirect-current energy 42 and a microphone transmitter 43. The terminalof the inductance coil 27 adjacent the tap point 26 is connected to anantenna 44.

In operation, the tubes 1 and 2 alternately serve as oscillationgenerators with successive alternations inthe polarity of the potentialsimpressed upon the anode elements 3 and 4 thereof. Hence, it can be seenthat both half cycles of the alternating currents lmpressed upon thesystem are employed for the generation of high-frequency currents. Theeffect of the sustaining induc-' tances, which are embodied in thetransformer windings 13 and 1-4,, is to prolong the power supply to onetube while that of the other tube is increasing to its maximum '58 ofthe transformer potential variations in the secondary windvalue, therebyremoving, to a great extent, the residual power fluctuations.

-Modulation of the radio-frequency currents generated by the oscillatortubes 3 and 4 is effected in a manner well known in'the art uponspeaking into the microphone transmitter 43. As hereinbefore stated, a

residual fluctuation in the radio-frequency wave of power frequency willremain, inasmuch as to obtain a perfectly uniform highfrequency wavewould necessitate the use" comprising anodes 47 and 48, grids 49 and 51and filaments 52 and 53, respectively, in shunt relation to secondarywindings 13 and 14, anodes 47 and 48 being connected to conductors 15and 16, respectively.

The filaments 52 and 53 are connected in parallel with the filaments 7and 8 of the oscillator tubes and energized from the common source ofenergy 9. The conductor 18, which serves to connect the severalfilaments to the common terminal 17 of the transformer secondarywindings, may include a primary winding 58 of a transformer 59. The gridelements 49 and 51 are connected, by a common conductor 61, to theseveral filaments. The conductor 61 may include a biasing source ofenergy 62, a secondary winding 63 of a modulating transformer 64 and aprimary winding 65 of the transformer 59, a resistor 66 being connectedin shunt relation to said primary winding 65 for a purpose hereinafterdescribed. A primary winding 67 of the modulating transformer 64 isincluded in a circuit which may contain, in addition, a direct-currentsource of energy 68 and a microphone transmitter 69.

This system is further distinguished from that of Fig. 1 in the meansfor supplying the sustaining inductance to the oscillator tube leads.Instead of relying entirelyv upon the transformer to supply thesustaining inductance, a special sustaining reactor 71 is providedcomprising a magnetizable core member 72 and a pair of magnetizingwindings 73 and 74, the latter being serially included in the anodeleads 15 and 16, respectively.

The residual fluctuations of power he quency which traverse the primarywinding 59 are translated into ing 65 thereof and impressed upon thegrid elements 49 and 51. The effect of such grid-potential variations isto produce such is equally effective when connected in s ant to thesecondary winding 58 thereof.

Vthen voice waves enter the microphone transmitter (59, the potentialsof the grids 4!) and 51 are modulated in accordance with the varyingintensity of the sound Waves.

During a one-half-cycle of the impressedelectromotive force, when the]tube 1 is functioning as an oscillator, the modulator tube 45 iseffective. whereas. during the next half-cycle, when the tube 2 isfunctioning as an oscillator, the modulator tube 46 becomes effective.The operation and circuit arrangement of this system are otherwise asindicated forthose of Fig. 1.

Referring to Fig. 3, the arrangement therein shown differ from that ofFig. 2 in the means for balancing out the residual power fluctuation. Anadditional pair of amplifier tubes and 76 are herein employed foramplifying the effects of the Imicrophone transmitter 69, as hereinafterdescribed. The additional amplifier tubes 75 and 76 comprise anodes 77and 78, grid electrodes 79 and 81, and hot cathodes 82 and 83,respectively, the latter being energized from a common source ofdirect-current energy 84.

The tubes are energized by means of a transformer 85 having transformerconnections similar to the transformer 12. Anodes 77 and 7 ,8 areconnected, by conductors 86 and 87 to opposite terminals of theseriesconnected secondary windings. 88 and 89 of the transformer 85. Thehot cathodes 82 and 83 are connected to the common transformer secondaryterminal by means of a comluetor 91. The primary windings 92 and 93 ofthe transformer 85 are serially connected, by conductors 94 and 95,tothe source of alternating-c1lrrent energy 11. The grid elements 7 9and 81 are connected, by a common conductor, to the hotcathode elements82 and 83, through 'a secondary winding 97 of a modulating transformer98, the primary winding 99 of which is serially included in a circuitcontaining, in addition, a source 100 of directcurrent energy and themicrophone transmitter 69.

The anodes 77 and 78 of the amplifier tubes 75 and 78 are connected, byconductors 101 and 102, to the grid elements 49 and 51 of the modulatortubes 45'and 46, through stopping condensers 103 and 104, respectively.The hot-cathode elements .82 and 83 of the am lifiertubes 75 and 76 areconnected to the aments 52 and 53,013 the moduletor tubes 45 and 46 andto ground by means of a ground conductor 10:"). The grid elements 49 and51-of the modulator tubes 45 and 46 may be given a negative bias bymeans of conductors 106 and 107 which extend from said grid elements tothe hotcathode elements 52 and and which ini clude a commondirect-current source of energy 108 and individual radio-frequency chokecoils 109 and 110, respectively.

In the system shown in Fig.8, the lowfrequency fluctuations of power inthe amplifier tubes 7 5 and 76 may be decreased by decreasing thesustaining'inductances of the transformer 85, the adjustment being suchthat the main power-frequency fluctuations obtaining in the oscillatortubes 1 and 2 will be eliminated;

en voice-waves enter the microphone, transmitter 69, the power suppliedto the oscillator tubes 1 and 2 is modulated during successivehalf-cycles of the impressed elec tromotive force, thereby causing theresultant high-frequency currents in the antenna system to becorrespondingly modulated, all as will be understood by those versed inthe art. The operation and circuit arrangements of this system areotherwise as indicated for that of Fig. 2.

The arrangement shown in Fig. 4 distin-' vguishes from that of Figrl inthat means have been provided, whereby the system may be employed forthe transmission of wireless telegraph signals In the severalarrangements shown, the effect of the sustaining inductance of thetransformer 12 supplying the oscillator tubes, or of the. reactor 71 issuch as to prevent sudden interruptions of the alternating-supplycurrents. Hence, certain switching systems of telegraphy, involving theopening of either the high-frequency or the low-frequency circuits toform the necessary dots and dashes, are ineffective.

In the arrangement shown in Fig. 4, to form the dots and dashes, Isimultaneously short-circuit a resistor 112, which is normal-o 1yincluded in circuit with the primary 'member 116 of a normally closedrelay 117.

y A normally open relay 118 is connected in shunt relation to theresist-or 112 by conductors 119 and 121.

The resistor 112, which may be any form of im edance device, is of suchimpedance that t 9 current supplied to the oscillator tubes land 2-issuitably reduced durin the non-signaling periods. Actuating win ings 122and 123 of the relays 117- and 118 are connected in scries-cirialitrelation by a conductor 121 and ground. The conductor 121 may include asource of energy 125 and a controlling key 126.

In operation, when the key 126 is closed, the relays 117 and 118 aresimultaneously energized to effect the short-circuiting of the resistor112 and the open-circuiting of the grid-condenser shunt pathlli i. r,The system now oscillates in a. well known manner. lVhen the key 126 isopened, the relays 117 and 118 are deenergized, with the result that thegrid condenser 36 is short-circuited and the resistor 117 renderedeffective to limit the current supplied to the oscillator tubes 1 and 2.The system is now in a non-oscillatory state. As can readily be seen,the telegraph signaling system embodied in Fig. 1 may be readily appliedto any of the foregoing wireless telephone systems-1.;-

Asa further modification, I have included,

in the shunt path 113, a source of ener '127, the effect of which is todecrease t e impedance of the plate circuits of the oscillator tubes andhence decrease the power loss therein when the system is renderednonoscillatory. I v I Inasmuch as the fluctuations in the supplycircuits may consist of harmonics-20f .power frequency, the balancing ofthe power fluctuations may be made more complete by including, in thesupply circuit to theoscillator tubes 1 and 2, inductance'devioes tunedto particular harmonics. For the purpose of illustration, I have shownone such inductance device 128 in the filament return circuit 18 asshunted by a variable condenser 129 whereby the inductance device 128may be tuned to the frequency of the harmonic which it is desired toeliminate.

While I have shown several embodiments of my invention, for the purposeof describing the same and illustrating its several applications, it isapparent that various changes and modifications may be made thereinwithout departing from the spirit of my invention and I desire,therefore, that only suchlimitations shall be imposed thereon as areindicated in the prior art or are specifically set forth in the appendedclaims.

I claim as my invention:

1. Ina radio signaling device, an electrontube oscillator, a source ofperiodic current supplying said oscillator, and meanswhereby the currentsupplied to said oscillator ismaintained substantially constant, saidmeans including a transformer having large inductive reactance.

2. In a radio signaling device, an electron-tube modulating device, anelectrontube oscillating device, a source of periodic current supplyingsaid devices and means whereby fluctuations caused by the peri'-.

electron tubes having plate, grid and filament elements, supplyconductors connecting said plates to opposite terminals of saidsecondary windings, and a common supply conductor connecting saidfilament elements to an intermediate point in said secondary winding,said secondary winding being so designed as to have a large inductivereactance, whereby the sum of the currents in said supply conductors ispractically a constant quantity at all times.

4. ,An electrical system comprising a source of alternating currents, atransformer} having-primary and secondary windingsflconductorsassociating said primary winding with said source, a pair of oscillatortubes having plate, grid and filament elements, supply conductorsconnecting said plates to opposite terminals of said secondary winding,2. common supply conductor connecting said filament elements to anintermediate point in said secondary winding, said secondary windingbeing so designed as to have a large inductive reactance,

-whereby the sum of the currents in said plate conductorsis practicallya constant quantity at all times, and means associated with said tubesfor causing the same to function as oscillation generators.

5. An electrical system comprising an alternating-current source ofpower, a air of oscillator tubes, means for so coup ing said oscillatortubes to said source of power that both half-waves of the impressedelectromotive forces may be employed, the resulting radio-frequencyoscillations being modulated in accordance with the frequency of saidsource of power, inductive reactance means for reducing fluctuations inthe supply to said tubes, whereby said modulation may be decreased, andmeans for balancing out the remaining part of said modulation.

6. An electrical system comprising an alternating-current source ofpower, a air of oscillator tubes, means for so coup ing said oscillatortubes to said source of power that both half-waves of the impressedelectromotiv'e forces may be utilized, the resulting radio-frequencyoscillations generated by said oscillator tubes being modulated inaccordance with the frequency of said source, inductive reactance meansfor reducing fluctuations in'the power-supply to said tubes, wherebysaid modulation troducing, in

means is practically eliminated, and means for insaid power-supply, amodulation comparable to .the resldual modulation and inphase-opposition thereto.

7 An electrical system comprising an alternatinga-urrent source ofpower,a pair of oscillator tubes. means for so coupling said oscillator tubesto said source of power that both half-waves of the 1m: pressedelectromotive forces may be utilized, the resulting radio-frequencyoscillations generated by said oscillator tubes being modulated inaccordance with the frequency of said source of power, induct vereactance means embodied in said coupling means and operating to reducefluctuations in the power supplied to said tubes,'whereby saidmodulation is practically eliminated, a pair of modulator tubesparallelly associated with said oscillator tubes. and means for somodulating the impedance of said modulator tubes as to oppose theresidualpart of modulation.

S. An electrical system comprising an alternating-cnrrent source ofpower, a pair of oscillator tubes, means for so coupling said oscillatortubes to said source of power that both half-waves of the impressedelectromotive forces may be utilized, the resulting radio-frequencyoscillations generated by said oscillator tubes being modulated inaccordance with the frequency of said source of power, 1nduct1vereactance for reducing fluctuations in the power supplied to said tubes,whereby said modulation is practically eliminated, a pair of modulatortubes parallelly associated with said oscillator tubes, means formodulating the .impedances of said modulator tubes in accordance withthe modulation but in phase-opposition thereto, and means for furthermodulating the impedances of said modulator tubes in accordance with asignal. a

9. A system for producing oscillations comprising analternating-currentsource of power, oscillator tubes connectedthereto,means for reducing fluctuations in the power supplied to said oscillatortubes, a slight residual fluctuation remaining, amplifier tubesconnected to said source, means for reducing fluctuations in the powersupplied to said amplifier tubes, a slight residual fluctuationremaining, and means for so associating the oscillator and the amplifiertubes as to balance the residual fluctuations of the amplifier tubesagainst the residual fluctuations of the oscillator tubes.

10. A system for producing oscillations comprising analternating-current source of power, oscillator tubes connected thereto,

means for reducing fluctuations in the power supplied to said oscillatortubes, a

slight residual fluctuation remaining, am-

plifier tubes, a transformer, connections for 1 pressed electromotiveforces, means associated with said connections for reducing fluctuationsm the power supplied to said amplifier tubes, a slight residual fluctuastion, and means for so associating said amplifier tubes and saidoscillator tubes as to balance the residual fluctuation in the amplifiercircuits against that in the oscillator circuits. I c 11. In anelectrical system, an alternating current source of power, oscillatortubes, a transformer for so coupling said source and said tubes as toadmit of the utilization of both half-waves of the impressedelect-romotive forces, means tending to substantially removefluctuations in the mwer-supply to said tubes, amplifier tubes, atransformer so coupling said amplifier tubes and said source as to-admitof the utilization of both half-waves of the impressed eleetromotiveforces, means tending to substantially remove fluctuations in the powersupplyto said amplifier tubes and means so associating the oscillatorand the amplifier tubes as to balance the amplifiertube residualfluctuations against the oscillator-tube residual fluctuations.

12. In an electrical system, an alternating-current source of power,oscillator tubes, a transformer so coupling said source and said tubesas to admit of the utilization of both half waves of the impressedelectro-.

motive forces, inductive reactance means embodied in said transformerfor substantially removing fluctuations in the power supplied to satubes, amplifier tubes, a transformer so coupling said amplifier tubesfier tubes, and means so associating the oscillator and the amplifiertubes as to balance the amplifier-tube residual against theoscillator-tube residual fluctuations.

,13. In an electrical system, an alternating-current power supply,oscillator tubes, a transformer so coupling said power in saidlast-mentioned transfluctuations supply and said tubes as to admit ofthe utilization of both half-waves of the impressed electromotiveforces, means tending to substantially remove fluctuations in the powersupply to said tubes, amplifier tubes, 1,25

a transformer 'so coupling said amplifier tubes and said power supply asto admit of the utilization of both half waves of the impressedelectromotive forces, means tending to substantially remove fluctuationsin the power supply to said am lifier tubes and means associating saidamp ifier tubes with the control elements of said modulator tubes,whereby the amplifier residual fluc tuations may be caused to balancethe oscillator residual fluetuation.

14. In an electrical system, an alternatingcurrent power supply, a pairof oscillator tubes, a modulator tube having a controlling electrodeparallelly associated with each oscillator tube, a transformer socoupling said power supply and said tube as to admit of the utilizationof both half waves of the impressed electromotive forces, a sustaininginductance embodied in said transformer winding tending to substantiallyeliminate fluctuations in the power supply to said tubes, amplifiertubes having control electrodes, means for supplying said amplifiertubes from said power supply with currents having residual fluctuationssimilar to those in said oscillator-tube circuits, circuit con-'nections for impressing said amplifier fluctuations upon said modulatorcontrol electrodes, whereby the residual fluctuations in said oscillatorcircuits may be eliminated, and means carrying modulating currentsassociated with said amplifier control electrodes.

In testimony whereof, I have hereunto subscribed my name this 23rd dayof March, 1922.

FRANK CONRAD.

